Electric control circuit



Feb. 5, 1946. I E, c. wAHLBER 2,394,029

- ELECTRIC CONTROL CIRCUIT I filed June 18, 1943 4 Sheets-Sheet 1 IN VEN TOR.

xam/4W Feb. 5, 1946. v Q E. WAHLBERG 2,394,029

ELECTRIC CONTROL CIRCUIT Filed June 18, 1943 4 Sheets-Sheet 2 h/djVENTo.

' ifiwwaw A TIDE/V51 Feb. 5, 1946. E, c. WAHLBERG ELECTRIC CONTROL CIRCUIT Filed June 18, 1943 4 Sheets-Sheet 3 INVENTOR. 3 7702MB) Feb. 5, 1946. a WAHLBERG 2,394,029

I ELECTRIC CONTROL CIRCUIT Filed June 18, 1943 v 4 Sheets-Shet 4 O g 4 U 9- k 9 no 9 9 $9 s Q 8 Q Q Q m in E W E1 9 g N m a; Q N Q g & g

3? $1 INVENTOR. E Q Q :9 4M

Patented Feb. 5, 1946 ELECTRIC CONTROL CIRCUIT Eric C. Wahlberg, Stamford, Conn., assignor to Electrolux Corporation, Old Greenwich, Conn., a corporation of Delaware Application June 18, 1943, Serial No. 491,282

11 Claims.

My invention relates broadly to means for interrupting an electric circuit whenever one of two or more moving members gets a predetermined amount out of synchronism with respect to the other moving members. The opening of the circuit may be employed for any desired purpose, such as to initiate corrective measures to reestablish synchronism, to operate a warning signal for informing the operator that one of the members is out of synchronism, or to stop the movement of the members.

More specifically, my invention contemplates means for preventing unequal opening or closing of the Wing flaps of an airplane. Further objects and advantages of my invention will be apparent from the following descriptions considered in connection with the accompanying drawings which form a part of this specification and. of which:

Fig. 1 is a wiring diagram showing an application of my invention for stopping the rotation of Fig. 4 is a wiring diagram of my invention as applied to three rotating members; and

Fig. 5 is a wiring diagram showing a modification of the arrangement illustrated in Fig.4

Referring more particularly to Fig. 1, reference characters A and B designate two synchronously operating direct current motors of the type dis' closed in my co-pending applications Serial No. 428,018 filed January 24, 1942 and Serial No. 472,464 filed January 15, 1943. As described in said applications, a plurality of direct current motors may be caused to operate in synchronism if similar points in the armature windings of the several motors are connected to each other through suitable slip rings. Also, the armatures of the several motors may be angularly positioned before starting by applying direct current across two similar points in the armature windings of the motors. After the motors have been positioned in this manner, the direct current supply to the aforesaid points in the armatures is interrupted and current is supplied through the commutators in the usual manner. Thereupon, the motors start and run in synchronism due to the onnections between the similar points in the several armatures. The motors may be stopped in synchronism and their armatures angularly positioned with respect 55 to each other by interrupting the current to the commutators and again applying direct current through the slip rings to the similar points in the armature. However, as far as the present invention is concerned, the motors A and B could be any type of synchronous motor.

As illustrated in Fig. 1, each of the motor is provided with a winding diagrammatically illustrated at 10, while leads l2 and I4 connect similar points on the armature windings with slip rings Hi and l 8, respectively. These slip rings are connected together by means of conductors and 22. These conductors are also connected to the normally closed contacts d and f of a rela R. The blades cooperating with contacts d and f are connected through conductors 24 and 26 with a suitable source of direct current which may be controlled by the double pole switch 28. The motors are provided with field windings 30 which are connected in parallel by means of the conductors 32 and 34 to the switch 28.

Commutator brushes 36 and 38 are provided for each motor and are connected in parallel through the conductors 40 and 42, respectively, with the normally open contacts 0 and e of the relay R.

Mounted on the shafts 44 of the motors A and B are contact carrying elements 46 and 48, respectively. As shown. each element is provided with four contacts in the form of segments 50, 52, 54 and 56 and 50', 52'. 54' and 56'. The segments 50 and 54 of element 46 are connected together and are connected to a slip ring 58, while the segments 50 and 54' of element 48 are connected together and to a slip ring 58'. Segments 52 and 56 are connected together and to a slip ring 60, while segments 52' and 56 are onnected together and to a slip ring 60. Slip rin s 58 and 58 are connected through a conductor 59, while slip rings 60 and 60 are connected by a conductor 6|. A brush or other suitable contact making means 62 of a peripheral width sufiicient to span the gap between segments cooperates with element 46 and is connected to ground. A similar brush 62' cooperates with the element 48 and is connected to one side of a suitable supply of electric current, such as the battery 64. The other side of the battery is connected through a manual switch 66 to the holding coil of the relay R. The other terminal of the holding coil is connected to the blade of the relay which cooperates with the contacts a and b. The contact a is connected through a conductor 68 to ground, while contact b is connected to ground through a push button type switch 10.

Brush 62' may be connected directly to ground through a manual switch 12, but this switch is normally left open and is closed only in the event that it is desired to cut the elements 46 and 48 out of the circuit and connect the battery 64 directly to ground.

The above-described device operates as follows:

In starting, the switch 28 is closed, thus supplying excitation current directly to the field windings 30 of the motors A and B. Current is also supplied from the line through the conductors 24 and 26, the closed contacts (1 and j, the conductors 22 and 20, the slip rings I8 and I6 and the leads l4 and I2 to the armature windings 10. This causes the armatures of the two motors to be angularly positioned, if they were not already positioned, so as to bring similar segments of the contact carrying elements 46 and 48 into contact with the brushes 62 and 62. As shown in the wiring diagram, segments 50 and 50 of the two elements are in contact with their respective brushes.

This serves to establish a circuit from ground through the brush 62, segment 50, slip ring 58, conductor 59, slip ring 58', segment 50 and brush 62 to one side of the battery 64. From the other terminal of the battery the circuit continues through the manual switch 66 and the holding coil of the relay R to the contact b. However, as long as push button switch I is open, the relay remains deenergized, but closing of the switch l0 completes the circuit to ground and the relay is energized. This causes the blade of the relay which is connected to the holding coil to close the contact a, thus establishing a holding circuit through the conductor 68, whereupon the push button switch It! may be opened without deenergizing the relay.

Actuation of the relay opens the contacts d and f and closes the contacts 0 and e. Consequently, the supply of direct current to the slip rings I6 and I8 is interrupted, while current is a supplied to the armatures through the commu tator brushes 36 and 38.

The motors now start in the usual manner and tend to run in synchronism due to the permanent connection provided by the conductors and 22 between the slip rings I6 and I8. Synchronous operation of the motors causes the elements 46 and 48 to rotate in synchronism. As soon as the elements have turned through approximately one-eight of a revolution from the position shown in Fig. l, the segments 56 and 56' or 52 and 52', depending upon the direction of rotation, come into contact with the brushes 62 and 62'. There is thus established a circuit from ground through the brush 62, the slip ring 60, the conductor BI, the slip ring 60 and the brush 62 to the battery. Inasmuch as the brushes 62 and 62 are wide enough to span the gap between the segments, no interruption in the holding circuit of the relay occurs, and as long as the two motors and their respective elements 46 and 48 rotate in synchronism, the relay remains energized.

However, if as a result of a large inequality in loads or for any other reason, one of the motors speeds up or slows down with respect to the other an amount sufficient so that the brush 82 is in contact with either the segments 50 or 54, while the brush 62' is in contact with either the segments 52' or 56, the holding circuit of the relay will be interrupted, with the result that the relay is deenergized. This interrupts the supply of current to the brushes 36 and 38, thus causing the motors to stop. At the same time, direct current is supplied to the slip rings I6 and I8, thus angularly positioning the motors. This, of course, brings the elements 46 and 48 back into the proper angular relationship, but the motors do not start up unless the push button switch I0 is manually closed.

If for any reason it is desired to operate the motors A and B, even though they will not run in synchronism, the switch I2 may be closed, thus cutting the elements 46 and 48 out of the circuit. Thereupon, if the push button switch I0 is closed, the relay R will be energized and will remain energized regardless of whether or not the motors and the elements 44 and 46 are rotating in synchronism.

The switch 66 is provided for the urpose of stopping and positioning the motors while they are running in synchronism. Of course, the motors could be stopped by opening the switch 28, but if this were done, the excitation current for the fields would be interrupted and no current would be supplied to the slip rings I6 and I8. By opening switch 66 while switch 28 remains closed, the relay R is deenergized so as to supply current to the slip rings I6 and I8 while the fields remain excited, thus positioning the armatures of the motors.

In Fig. 2 there is shown a wiring diagram suitable for controlling the flap motors for an airplane. Again the motors are designated by the reference characters A and B and are provided with slip rings I 6 and I8 connected together by means of conductors 20 and 22, while the armature brushes 36 and 38 of the motors are connected in parallel by means of conductors 40 and 42.

Each motor is connected through a gear box with suitable linkage 82 connected to pivot a wing flap 84 which is mounted on a shaft 86.

Fixed to the two shafts 86 are contact carrying elements 88 and 90, which correspond to the elements 46 and 48 shown in Fig. 1, except that they are provided with a relatively large number of contacts or segments and are similar in appearance to commutators. These segments are connected in three groups, every third segment being connected in the same group. Thus, segments 92 are all connected together to form one group, segments 84 are connected together to form another group and segments 96 are connected together to form the third group. Due to the fact that the wing flap turns through a. maximum angle of about 55, it is not necessary to provide slip rings, but flexible leads 98, I00 and I02 may be employed for connecting the respective groups of segments to conductors I04, I06 and I08 which in turn are connected to similar flexible leads 98, I00 and I02 for the element 90. The elements are provided with brushes I I0 and I I0, respectively, which are wide enough to span the gap between adjacent segments but are not wide enough to be in contact with three segments at any given instant.

The relay circuit comprising the relays R1, R2, R3, R4 and 'I'Ri is similar in most respects to that disclosed in Fig. 2 of my co-pending application Serial No. 484,531 filed April 26, 1943. It includes a current supply line H2 connected to the blade of a single pole double throw switch II4 having contacts H6 and I I8. Contact H6 is connected by means of a conductor I20 with one terminal of the holding coil of relay R4, the other terminal of which coil is connected by a conductor I22 with the brush IIO of contact carrying element 88. Contact I I8 of the double throw switch is connected by means of a conductor I24 with the holding coil oi the relay R1, the other terminal of which coil is likewise connected to the brush IIO by means of the conductor I22. The brush N of contact carrying element 90 is grounded, and a manually operable switch I26 is provided for connecting the holding coils of relay Re and R4 directly to ground if it is desired to cut the elements 08 and 30 out of the circuit.

The line H2 is connected directly to the blade of relay R: which cooperates with the contacts Rae. and Rat. Contact Rae is connected by means of a conductor I28 with the normally open contact Rn oi. relay R4 and with the normally open contact R20. of a relay R2. The conductor I20 is also connected to the normally closed contact TR of thermal relay 'I'Ri. The blade of this relay is connected by a conductor I30 with one terminal of the holding coil of the relay R2, the other terminal of which is grounded.

The normally closed contact R3 of relay R3 is connected by a conductor I32 with the blade of relay R4 which cooperates with contacts Rn and R4!)- A conductor I34 connects normally closed contact R4b with the normally open contact Ran of relay R2. The blade of this relay which cooperates with contact Rn, is connected through a conductor I36 with one terminal of the holding coil of relay R1, the other terminal of which is grounded. Conductor I38, is also connected to one terminal of the heating coil of the thermal relay TR1, the other terminal of which is grounded.

The blades of relay R1 are connected to the opposite sides of a current sup l line I38. The" normally open contacts R and Rio are connected to the conductors 22 and respectively, which lead to the slip rings I3 and I6 of the motors A and B. The normally closed contacts Ru, and Rm are connected by conductors I40 and I42 to the normally open contacts R34 and RBc, respectively, of relay R3 and to the normally open contacts Rid and R40, respectively, of relay Rt. Conductor 40 is connected to the blade of relay R4 which cooperates with contact Rie and with the blade of relay R3 which cooperates with contacts Ran and R3e, while conductor 42 is connected to the blade of relay R4 which cooperates with contacts Rid and R48 and to the blade of relay Ra which cooperates with contact Rsc. Contacts Rae and Rie are connected together by a conductor I44.

One side 01' each of the field windings is grounded, while the other side is connected by means of a conductor I46 to the normally open contact R20 of relay R2. The blade which cooperates with contact Rae, as 'well as the blade which cooperates with contact Rza are connected direct- 13' to the line H2.

The above-described device operates as follows:

When the pilot desires to open the wing flaps 84 and 84, he throws the switch I I4 to the lowermost position, thus supplying current from the line I I2 through the contact I I6, and conductor I20 to the holding coil of the relay R4. From here the circuit is completed through the line I22, the brush IIO, segment 92 of contact carrying element 88, flexible lead 98, conductor I04, flexible lead 08, segment 92' and brush I I0 to ground. Relay R4 i thus energized and contact R4 is closed. Current is consequently supplied from line II 2 through normally closed contact Rab, conductor I32, contact Ra, conductor I28, contact TR, and conductor I30 to the holding coil of relay R2. Inasmuch as the other side of this coil is permanently grounded, the coil is energized so as to close contacts Rn, Rzb, and R20. Closing of the last-mentioned contact supplies current from the line II2 through the conductor I40 to excite the field windings 30.

Relay R1 remains deenergized for, although contact Rob is closed, contact R4 is opened and consequently, no current is supplied to the holdlng'coil of relay R1. Current therefore flows from the line I38 through the blades of this relay and through the normally closed contacts R11: and Rm and the conductors I40 and I42 to the closed contacts R44 and R412, respectively. From here the current flows through the conductors 42 and 40, respectively, to the brushes 36 and 38 of the motors A and B. The motors are thus caused to rotate in a direction such as to open the flaps 84 and 84' through the mechanical connection constituting the gear reduction units and 80 and the linkage 02 and 32, respectively. If the mechanism is operating properly, the motors A and B run in synchronism and consequently the flaps 84 and 04' open together. This causes the elements 88 and 90 to rotate in synchronism with the result that, assuming the elements to rotate in a counterclockwise direction, the circuit between the brushes H0 and H0 is completed first through a segment 02, conductor I04 and segment 92, then through a segment 94, conductor I06 and segment 94', then through a segment 96, conductor I08 and se ment 96, and through another segment 92, conductor I04 and another segment 92 and so forth. Due to the fact that the brushes H0 and H0 are broad enough to span the gap between adjacent segments, there is no interruption in the circuit as long as the elements rotate in synchronism. However, should one of the elements get out of angular phase relation with respect to the other so that the brush H0 is in contact with, for instance, a segment 94, at the same instant the brush H0 is in contact either with a segment 92 or 36' the circuit will be open, thus deenergizing relay R4, which serves to stop the motors A and B in a manner to be subsequently described.

It is preferable to have three groups of contact segments, instead of the two groups shown in Fig. l, in order to prevent the circuit from remaining closed in the event that one of the flaps does not open at all. It might be that the mechanical connection between one of the motors and its flap has been damaged to such an extent that the motor may run without actuating the flap. Moreover, the flap might be in such a position that the brush H0 or IIO spans two adjacent'segments. In such an event, if there were only two groups of segments, the circuit through the contact carrying elements would not be interrupted even through one element did not rotate at all. However, by providing three groups of segments connected by means of the three conductors I04, I06 and I08, this condition cannot obtain and an open circuit will occur after one of the elements has rotated through an angle not greater than that occupied by three segments- I If the circuit through the elements 38 and 90 is interrupted and the relay R4 thus deenergized, contact Rn is opened and contact Rdb is closed. Consequently, current from the line II2 passes through contact RBb, conductor I32, contact Rab, conductor I34, contact R219, and conductor I36 to energize relay R1 and to heat the coil of thermal relay 'IRi. Relay R2 remains energized due to the holding circuit provided from the line II2 through the contact R2a, contact 'I'Rrr, and conductor I30, even though the contact Rd is now open.

Energizatio-n of relay R1 opens the contacts Rib and Bid, thus interrupting the flow of current from the line I38 to the conductors I40 and I42 and consequently the brushes 3B and 38 of the motors A and B are disconnected from the line.

Closing of the contact Rie serve to short circuit the armature leads 40 and 42 of the motors A and B, thus dynamically braking the motors and bringing them to a quick stop. At the same time, contacts Rla and Rio are closed and current from th line I38 is supplied through these contacts to the conductors 22 and and the slip rings I8 and IS. The fields 30 remain excited, inasmuch as contact RZc remains closed, and con sequently, the motors A and B are angularly positioned.

After a predetermined length of time the heat ing of the coil of thermal relay TRi causes the contact TRla to open, thus opening th holding circuit of relay R2 and deenergizing this relay. This opens contact R20, which interrupts the supply of current to the field windings 30. Contact R2b is also opened, thus interrupting the supply of current through the conductor I36 to relay R1 and to thermal relay 'IRi. Consequently, both of these relays are deenergized. Contacts Rla and Rio are thereupon opened and the supply of current from the line I38 to the slip rings i 5 and I8 is interrupted. At the same time, contacts Rib and Rld are closed but this does not result in connecting the brushes 3B and 38 to the line because contacts R-lc and Rid and R30 and RSd remain open.

If the flaps 34 and 84 open in synchronism, the elements 88 and 90 do not interrupt the holding circuit of relay R4 and the fiaps continue to open until they have reached the desired angle of, for instance, 55 if they are landing flaps, or if they are diving flaps. When the desired angle has been reached, so-called limit switches I 48, which are connected in series in the conductor I20, are opened, thus deenergizing relay R4. Thereupon, the same sequence of operations takes place as previously described when the relay was deenergized because of the elements 88 and 9!! getting out of synchronism.

When it is desired to close the wing flaps, the pilot throws the switch II4 to its uppermost position, thus supplying current to the holding coil of relay R3 through the contact H9 and conductor I24. Th holding circuit for this relay is completed through conductor I 22, and the elements 88 and S0 in the same manner as previously described, so long as the elements turn in synchronism. Actuation of relay R3 closes contacts R321, R and R3d and current is supplied from the line II2 through contact R321, conductor I28, contact TRla and conductor I30 to energize relay R2. The operation of the control circuit is the same as that previously described except that conductors I40 and I42, carrying current from the line I38, are connected through closed contacts R3d and R30, respectively, to conductors 40 and 42. Consequently, the polarity of conductors 42 and 40 is reversed with respect to their polarity when the relay R4 was energized, and, inasmuch as the polarity of the field coils 30 has not been reversed, the motors A and B run in the opposite direction so as to close the flaps. If the fiaps close together, the holding circuit through the element 88 and 90 is not interrupted and the motors continue to operate until the flaps are fully closed, whereupon limit switches I43 open the circuit. However, if the flaps for any reason do not close in synchronism, the circuit through the elements is interrupted, and both flaps remain open at substantially the same angle.

It will thus be seen, that with the arrangement illustrated in Fig. 2, it is impossible to open or close one flap unless the other flap is opened or closed a like amount. This is of great importance because, if one flap should open while the other remains closed, it would tend to throw the ship into a spin from which it would be difficult to recover, particularly at the low altitude at which the landing flaps are usually opened. It would be much better to have neither of the flaps open, which would merely mean that the ship would have to land at a higher speed than ordinarily.

If desired, the switch I26 may be provided for cutting the contact carrying elements 88 and 90 out of the circuit, which might be desirable it merely the elements themselves or the conductors I04, I06 and I08 connecting them were damaged. If, with the switch I26 open as it normally would be, the pilot throws the switch I I4 to open the landing flaps and the flaps do not open, he could go up to a safe altitude and then close the switch I26. If the damage is in one of the motors, the gear unit or the linkage connected to the flap, this will result in one of the flaps starting to open, while the other would remain closed. The pilot would immediately be aware of this because of the reaction of the ship and would be ready to instantly cope with it by throwing switch I I4 to the opposite position to close the flap which had started to open. Due to his altitude, he would have ample opportunity to regain control of the ship after the fiap closed. However, if the damage was only in the contact carrying elements or in the conductors I04, I06 and I08, both flaps would open together and the ship could be landed with them open.

Instead of mounting a rotary contact carrying element on the shaft 86 of the wing flap, as 11- lustrated in Fig. 2, the fiap may be arranged so that pivoting thereof causes straight line motion of an element provided with a plurality of contacts or segments, as shown in Fig. 3. Thus, the flap 84 which is pivoted on the shaft 86 has attached thereto a member which carries a pin 81 slidable within a curved slot 89 formed in an arm 9|. Arm 9| is fixed to an element 93 which is slidably mounted in a suitable housing 95. A plurality of equally spaced segments 91, 99 and IN are suitably mounted in the element with their upper surfaces flush with the bottom of a groove I03. The element 93, or at least that portion which carries the segments is preferably made of insulating material. The groove I03 is provided so that the segments cannot contact the casing 95, which may be of metal, when the element slides through a suitable opening in the casing.

As was the case in the embodiment illustrated in Fig. 2, every third segment is connected together, whereby there are three groups of segments. Flexible leads 98, I00 and I02 connect the three groups to the conductors I04, I06 and I08, respectively. A brush I05, carried by a suitable brush holder I01, enters the groove I03 so as to contact the segments as the element 03 is moved, and is connected to the conductor I22.

Devices like that shown in Fig. 3 could replace the rotary elements 88 and 90 of Fig. 2. As the wing flap pivots about the shaft 86 in a clockwise direction, it causes the element 93 to move to the right, thus. causing: the segments to slide under the brush I05. In the position shown the brush is in contact with one of the segments 81 and consequently the circuit is completed from the conductor I22 through the brush I05, the segment 91, the flexible lead I02 and the conductor I08. which leads to a similar device connected to the other wing flap. A slight movement of the element 93 to the right establishes a circuit through a se ment 98, the flexible lead I and the conductor I06, while iurther move ment establishes a circuit throu h a segm nt I 1, flexible lead 98 and conductor I04.

Consequently, as long as the two wins fl il-Fl move in unison, the circu t remains closed. the same manner as described in connection with Fig. 2. Howev r. should one flap t ou of angular phase relationship w th resp ct to the. other by an amount suflicient to cause the brushes in the different devices to contact segments of ifierent groups. an o n c rc t esu ts and th relays of Fig. 2 operate in the manner previously described to stop both motors.

In Fig. 4, there is illustrated an arrangement whereby any number of contact carrying elements may be connected together in such a way that asynchronous rotation of any one of them will open a circuit. The elements are designated by reference characters I50, I50 and I50. Each is provided with a single segment I52, I52' and I52 extending through an arc of a little more than 120. Associated with each element are three pairs of brushes, those associated with ele? ment I50 being designated I54, I56 and I58, I80, and I62, I64. Brushes I54, I60 and I62 are connected to a conductor I65, Brush I56 is con, nected by means of a conductor I68 to a brush I58 associated with element. I50. Brush I58 is connected by means of a. conductor I to a brush I58, while brush I64 is connected by means of a conductor I12 to a brush I54. Brushes I54, I60 and I62 are connected by means of conductors I14, I16 and I18 to brushes I54, I60 and I62, respectively, associated with element I50". The remaining brushes I56, I58" and I64" are connected to a conductor I80,

With the elements in the position shown in Fig. 4, a circuit will be completed from conductor I66 through brush I54, segment I52, brush I56, conductor I68, brush I56, segment I52, brush I54, conductor I14, brush I54", segment I52", and brush I56" to conductor I80. No circuit will be completed through any of the other brushes inasmuch as none of them is in Contact with a segment. c

When the respective elements have rotated, for instance, in a clockwise direction as indicated by the arrows, through an arc suflicient to bring the segments I52, I52'and I52" into contact with the brushes I62 and I64, I62 and I64 and. I62" and I64", the circuit between conductors I66 and I80 will be through these brushes and the conductors I12 and I18. Due to the vfact that the segments subtend an arc of slightly more than 120, this latter circuit will be established before the former is interrupted.

A rotation of another 120 brings the segments into contact with the brushes I50 and I60, I58 and I60,. and I58" .an,d I60" and consequently, a circuit is established through these brushes and the conductors I10 and I16.

However, should any one of the elements get out of ,synchronism with respect to the other to such an ext nt that, at any g en inst nt. its segment contacts a of brushes whic do not correspond to he n on cted y he se ments or the other ele n a op n cuit results. Due to the fact that there are three pairs of brush s associa ed w h e c elem nt. is. imposs ble i r one e ement t r ma n n a stationary pos io con ac in l t rus D e. to the fact tha ere mus e an over ap between successive pairs of brushes in order to avoid momenta y p n n o th c rc i u n synchrono s opera i n. i wou d e o s bl for one or more elements to remain at rest in C011}.- act with all the br s e if on y tw pair of ru hes were emp ed- It will be seen that with the arrangement illustrated in Fig. 4, the circuit between the conu ters, I66 and I w l not e o ned u e one of he contact carr g l me s s s app oximatel 20" out o an ula alignment w t respect to the other elements. If it is desired to o en the c cuit wh n an e m n is out o ansu lar a gnment by a less mo a plu a ty of relati el na ow nt c s r se n s may be mployed, as i lustra ed n F 5. Eleme s 2, 82 nd L82" a e p ov d r sp t y wi e m nts I84 thr u .202. 1 rou h 20 and 84" throu h 02"- B sh 20 1203, 0. 212 and 4 re aswiated w t element I82 a d are a ran ed in pa rs, as shown n 5, the brushes Of each pair being in axial alignment. Similar brushes 2.04, 20.6, 208', 2I0', 2I2, and 2I4' are associated with element I82 while brushes 20.4, 206", 208", 2I0, 2I2-" and 2I4' are associated with element I82". A conductor 2I6 is connected to brushes 20,4, 208 and 2I2. Brushes 206 and 206, 2I0 and 2I0', and 2I4 and 2M are connected together by conductors 2I8, 220 and 222, respectively. Brushes 204' and 204 2.08 and 208, and 2I2 and 2I2" are connected together by means of conductors 22,4, 226 and 220-, respectively. A conductor 230 is connected to each of brushes 206", 2I0 and 2I4.

The segments in the elements are so spaced that one pair of brushes makes contact with a segment just before contact is broken between another pair of brushes and another segment. In Fig. 5, the brushes 204 and 206 are shown in contact with the segment I84 and consequently are connected through this segment. Assuming the commutator to be rotating in the direction indicated by the arrow, it will be seen that the segment I will make contact with the brushes 20,8 and 2I8 before segment I84 has passed out of contact with brushes 204 and 206. Likewise, segment I96 will come into contact with brushes H2 and :2I4 before segment I90 has passed out of contact with brushes 208 and 2I0. ons u nt as lens s he ra l en rotate together, a circuit will remain closed between the conductors 2I6 and 230.

However, should one of the elements get out of angular alignment with respect to the others by an amount equal to the width of a brush plus the width ,Of a segment, the circuit will be opened at such element. Thus, if the element I82 is in the position shown in the figure, while the element I182 is ahead of the position shown by an amount sufiicient to bring the segment I 84 out of contact with the brushes 204 and 206, the circuit will be opened at the element one element gets out of proper angular relationship with respect to the others. The circuits shown in these figures may be employed to stop the motors in a manner similar to that shown in Figs. 1 and 2, or the circuits may be employed to operate warning devices or to initiate corrective measures or to perform any other desired function.

While I have shown several embodiments of my invention, it is to be understood that this has been done for purposes of illustration only and that the scope of my invention is not to be limited thereby, but is to be determined by the appended claims.

What I claim is:

1. In a device of the class described, a plurality of contact carrying elements movable in unison, contact makin means associated with one of said elements, a plurality of conductors for connecting the contacts of said elements in series, the first-mentioned element successively connecting said conductors to said contact making means, and contact making means associated with the last element in the series, said last mentioned element successively connecting said conductors to the last-mentioned contact making means in timed relationship to the connections established by the first-mentioned element so long as the elements move in unison.

2. In a device of the class described, a pair of rotatable members, means for rotating said members in synchronism, a contact carrying element rotatable with each of said members, each of said elements having a like number of contacts, a plurality of conductors for permanently connecting together corresponding contacts in the two elements, a brush associated with one of said elements, the one element successively connecting said conductors to said brush, and a brush associated with the other element, said other element successively connecting said conductor to the last-mentioned brush in timed relationship to the connections established by said one element as long as the elements rotate in synchronism.

3. In a device of the class described, a pair of rotatable members, means for rotating said members in synchronism, a contact carrying element rotatable with each of said members, each of said elements having a like number of contacts connected in a plurality of groups, adjacent contacts being connected to difierent groups, a conductor permanently connecting together corresponding groups in the two elements, a brush associated with one of said elements, the one element successively connecting said groups to said brush, and a brush associated with the other element, said other element successively connecting said groups to the last-mentioned brush in timed relationship to the connections established by said one element as long as the elements rotate in synchronism.

4. In a device of the class described, a pair of rotatable members, means for rotating said members in synchronism, a contact carrying element rotatable with each of said members, each of said elements having a like number of contacts connected in at least three groups, adjacent segments being connected to different groups, a conductor permanently connecting together corresponding groups in the two elements, a brush associated with each of said elements and having a width suflicient to span adjacent contacts and less than the minimum distance between alternate contacts, said elements successively and simultaneously connecting corresponding groups to the respective brushes as long as the elements rotate in synchronism.

5. In a device of the class described, a plurality of movable members, means for moving said members in unison, a contact carrying element movable in a straight line by each of said members, each of said elements having a like number of contacts, a plurality of conductors for connecting the contacts of said elements in series, contact making means associated with one of said elements, the one element successively connecting said conductor to said contact making means, and contact making means associated with the last element in the series, said last element successively connecting said conductors to the last-mentioned contact making means in timed relationship to the connections established by the said one element so long as the elements move in unison.

6. In a device of the class described, a plurality of synchronous electric motors, a contact carrying element movable by each motor, contact making means associated with one of said elements, a plurality of conductors for connecting the contacts of said elements in series, the firstmentioned element successively connecting said conductors to said contact making means, contact making means associated with the last element in the series, said last element successively connecting said conductors to the last-mentioned contact making means in timed relationship to the connections established by the first-mentioned element so long as the elements move in unison, and means operative by the opening of the circuit between said contact making means for stopping said motors.

7. In a device of the class described, a pair of synchronous electric motors, a contact carrying element rotatable by each of said motors, a plurality of conductors for permanently connecting together corresponding contacts in the two elements, a crush associated with each of said elements, said elements successively and simultaneously connecting corresponding contacts to the respective brushes to maintain a closed circuit between the brushes as long as the elements rotate in synchronism, and means operable by the opening of the circuit between said brushes for stopping said motors.

8. In a device of the class described, a plurality of contact carrying elements movable in unison, a plurality of pairs of brushes associated with each element, the brushes in each pair being arranged to be periodically connected together by the contacts of the respective elements, said connection in difierent pairs associated with the same element being established successively, means for connecting together one brush of each pair associated with one of said elements, means for connecting together one brush of each pair associated with another element, and means for interconnecting each of the otherwise unconnected brushes associated with each one of said elements with an otherwise unconnected brush of a corresponding pair associated with a single other element.

9. In a device of the class described, at least three contact carrying elements movable in unlson, a plurality of pairs of brushes associated with each element, the brushes in each pair being arranged to be periodically connected together by the contacts of the respective elements. said connection in different pairs associated with the same element being established successively.

means for connecting together one brush of each pair associated with the first of said elements, means for connecting together one brush of each pair associated with the last of said elements, and means for connecting each of the remaining brushes associated with said first element with a brush of a corresponding pair associated with an intermediate element, and means for connecting each of the remaining brushes associated with said last element with an otherwise unconnected brush of a corresponding pair associated with an intermediate element.

10. A device as set forth in claim 8 in which the contact carrying elements are rotatably mounted cylinders and both the pairs of brushes and the individual brushes in each pair are disposed circumferentially around the respective elements.

11. A device as set forth in claim 8 in which the contact carrying elements are rotatably mounted cylinders and the pairs of brushes are disposed circumferentially around the respective elements, the brushes in each pair being spaced axially.

ERIC C. WAHLBERG. 

